Cholecystokinins (CCK) are a family of amino acid polypeptide hormones. CCK.sub.33, a 33 amino acid fragment of CCK was first isolated from hog intestine. (Matt and Jorpes, Biochem. J. 125 628 (1981)). Recently the CCK.sub.33 fragment has been found in the brain, where it appears to be the precursor of two smaller fragments, an octapeptide CCK.sub.8 and a tetrapeptide CCK.sub.4. (Dockray, Nature 264 4022 (1979)).
CCK.sub.8, the carboxyl terminal octapeptide fragment of CCK, is the most potent peptide in the CCK family and is the predominant form of CCK in the brain. (Larson and Rehfeld, Brain Res. 165 41 (1981)). The localization of CC fragments in the cortex of the brain suggests that CCK may be an important neuromodulator of memory, learning and control of primary sensory and motor functions. CCK and its fragments are believed to play an important role in appetite regulation and satiety. (Della-Fera, Science 206 471 (1979); Gibbs et al., Nature 289 599(1981); and Smith, Eating and Its Disorders, eds., Raven Press, New York, 67 (1984)).
CCK antagonists are useful in the treatment and prevention of CCK-related disorders of the gastrointestinal (GI), central nervous (CNS) and appetite regulatory systems of animals, especially man. CCK antagonists are also useful in potentiating and prolonging opiate induced analgesia and thus have utility in the treatment of pain. (Faris et al., Science 226 1215 (1984)).
Previously four distinct chemical classes of CCK receptor antagonists have been reported. The first class comprises derivatives of cyclic nucleotides as represented by dibutyryl cyclic GMP (N. Barlos et al., Am. J. Physiol., 242, G 161 (1982) and references therein). The second class is represented by C terminal fragments of CCK (see Jensen et al. Biochem. Biophys. Acta, 757, 250 (1983) and Spanarkel J. Biol. Chem. 758, 6746 (1983)). The third class comprises amino acid derivatives of glutamic acid and tryptophan as indicated by proglumide and benzotript (see Hans et al. Proc. Natl. Acad. Sci. U.S.A., 78, 6304 (1981) and Jensen et al. Biochem. Biophys. Acta. 761, 269 (1983)). The fourth and most recent class is comprised of 3-substituted benzodiazepines, represented by L-364, 718 (see: Evans et al. Proc. Natl. Acad. Sci. U.S.A., 83 4918 (1986)).
With the exception of the benzodiazepine based class, all of these compounds are relatively weak antagonists of CCK demonstrating IC.sub.50 values between 10.sup.-4 and 10.sup.-6 M. The benzodiazepine CCK antagonists or their metabolites may have undesirable effects in vivo due to their interaction with benzodiazepine receptors.
The C-terminal pentapeptide fragment of CCK is the same as the C-terminal pentapeptide fragment of another polypeptide hormone, gastrin. Gastrin, like CCK, exists in both the GI and CNS systems. Gastrin antagonists are useful in the treatment and prevention of gastrin-related disorders of the GI system such as ulcers, Zollinger-Ellison syndrome and central G cell hyperplasia. There are no known effective receptor antagonists of the in vivo effects of gastrin. (Morely, Gut Pept. Ulcer Proc., Hiroshima Symp. 2nd, 1, (1983)).